So far, for example, Patent Document 1 discloses a combustion control apparatus for an internal combustion engine. This conventional combustion control apparatus detects abnormal combustion (pre-ignition) on the basis of the output of in-cylinder pressure for detecting the in-cylinder pressure. Further, when a pre-ignition is detected, retard of ignition timing or enrichment of an air fuel ratio is performed in order to suppress the pre-ignition.
Including the above described document, the applicant is aware of the following documents as related art of the present invention.